Security chiefs from both the Republic and the UK will meet in the coming days to plan a major operation to protect Queen Elizabeth, Prince Philip, the Duke of Edinburgh, and their entourage.

An Garda Siochana is expected to cancel all leave during the two-day trip, the first state visit to the Republic by a British monarch.

The Metropolitan Police from London will provide a royal-protection squad and will travel with the monarch at all times. Garda special units, including the Emergency Response Unit, will provide close protection, while the Army Ranger Wing and snipers will be deployed for close protection of residences where she will stay, most likely Farmleigh House.

It is believed that the Queen will land at Baldonnel airbase, while a no-fly zone will be in effect over Farmleigh House and the airbase will be patrolled by armed Air Corps PC-9 planes.

A cavalcade is expected to move the royal party from place to place as the Queen is said to dislike helicopters.

A number of sources said earlier this month the Queen would make a "major" speech in Dublin Castle.

British Ambassador Julian King said: "The invitation symbolises how far the relationship between the two countries has come and the progress that has been made in Northern Ireland."

It has also emerged that Pope Benedict could visit Ireland in September and a visit by President Obama is due later in the year.